(1) Field of the Invention
This invention relates to novel compounds and methods for increasing the efficiency of feed utilization in animals, particularly ruminant animals.
More specifically, this invention relates to feed additives for ruminant feed compositions which alter rumen metabolism to result in inhibition of methane production and an increase in propionate production relative to acetate.
(2) State of the Art
The improvement of feed efficiency of ruminant animals has for many years been a highly desirable commercial objective. The economic incentive is clear. If a method is devised for increasing feed efficiency and/or the rate of weight gain of cattle or sheep while decreasing the amount of feed consumed by these animals, then the farmer's costs for raising these animals are reduced.
In order to improve the efficiency of feed utilization by ruminants, first it was necessary to discover and understand the mechanism by which these ruminants digest the various components of their feed and to determine the resultant digestion products which are metabolically utilized by the animal. As a result of extensive work in this area, the mechanism for carbohydrate utilization by ruminant animals is well known and documented in the literature. Raun in his U.S. Pat. Nos. 3,790,667, 3,790,668, 3,794,732 and 3,839,557, the disclosures of same are herein incorporated by reference, clearly sets out what is recognized as the accepted mechanism for the utilization of the feed carbohydrates by ruminant animals and further discloses the relevant references teaching the early work conducted in this area of technology. Raun found that propionate production could be increased and in turn improve ruminant feed utilization by orally administering to the ruminants selected polyether antibiotics and such physiologically-acceptable compounds, as thiostrepton, monensin and dianemycin. It is also pointed out in the Raun patents that inducing an increase in propionate production in the rumen of the animal results in a secondary benefit apart from the increase in feed utilization efficiency. The secondary benefit being the inhibition of ketosis which is the result of a high proportion of acetate in the rumen and which amounts to a clinical illness in the animal.
Since Raun's work, further studies have been conducted investigating the effect of monensin, in particular, on rumen metabolism, e.g., Van Nevel, et al., Appld. and Envl. Microbio., 34(3), pgs. 251-257 (Sept. 1977) and Slyter, Appld. and Envl. Microbio., 37(2), pgs. 283-288 (Feb. 1979). In addition, others have found that such additives as polyhalohemiacetal derivatives of saccharides and polysaccharides, Parish, et al., U.S. Pat. No. 3,615,649 and polyhaloalkamines, Parish, et al., U.S. Pat. No. 3,733,417, can improve the feed efficiency of ruminant animals. None of these feed additives, however, have proven to achieve the optimum results with respect to preventing the animal from reducing feed intake while at the same time inducing the optimal increase in propionate production in the rumen of these animals over an extended period of time.